Before we start to build the entire flow we need to draw splines representing guides where you want to plant objects on. Keep in mind to turn the interpolation steps of each spline to 0 otherwise you'll end up with a damn lot of vertices! ;)

Now add a Normalize Spline modifier from the Modifier List.

Right Click all of your splines and check Vertex Ticks in the Display Properties. Now you can see every vertex on the spline. The spacing between every vertex is set by the Segment Length of the Normalize Spline modifier, that's why we need it!

Now convert your spline into an edit poly by right clicking it and using the Convert To operation. NOW you if you didn't set the interpolation steps to 0 you will have a lot of vertecies. We don't want that! The interpolation steps insert the amount of steps into each space...